In particular, the present invention finds advantageous, but not exclusive, application in industrial ceiling fans operated by a permanent magnet motor with electronic control and supplied with single-phase alternating voltage, to which the following description will make explicit reference without thereby losing its generality.
Industrial fans must typically operate continuously throughout the day and must be characterised by a remarkable reliability in order to operate for several years. Such fans typically comprise a permanent magnet motor electronically controlled by a power supply and drive device, which in turn is supplied with a single-phase alternating voltage and comprises in cascade, in the following order, a full-wave voltage rectifier stage to provide a rectified voltage, a power factor corrector stage, a smoothing capacitor for smoothing the oscillations of the rectified voltage and providing a dc voltage having a residual periodic oscillation, otherwise known as ripple, with a limited amplitude, and a motor drive stage, which is supplied with the dc voltage and is typically constituted by an inverter, i.e. a DC-AC converter, controlled by appropriate PWM signals.
The smoothing capacitor is an electrolytic capacitor, since only an electrolytic capacitor may have such a high electrical capacity to guarantee a ripple with a contained amplitude. Unfortunately, the electrolytic capacitor loses its electrical characteristics after a few years, typically after 7-8 years, and consequently causes a degradation of the characteristics of the whole power supply and drive device.